import os'''#作业：输入用户名和密码#认证成功后显示欢迎信息#超过3次锁定'''for i in range(3):    i +=1    username = str(input("username:"))    password = str(input("password:"))    if username == "admin" and password == "admin@123":        print("登录成功")        exit()    else:        print('登录失败，还剩下%d次机会\n' %(3-i))exit("超过3次，请稍后再试！！！")'''##或者用while实现i=1while i <= 3:    i += 1    username = str(input("username:"))    password = str(input("password:"))    if username == "admin" and password == "admin@123":        print("登录成功")        exit()    else:        print("登录失败%d!\n" %(4-i))else:    print("登录失败，请稍后再试")##"https://www.bilibili.com/video/av13690129?p=31"'''